Replication itself can cause errors in the DNA sequence that is not always detected during the cell cycle checkpoints. These errors put the cell at risk of developing into a cancer cell. In order to protect genomic integrity there are a few cells that rarely replicate and act as the progenitor cell for all other cells, these cells are called stem cells. These stem cells maintain the original copy of DNA (conserved strand) during each replication event. By ensuring these cells rarely replicate and when they do replicate they keep the conserved strand of DNA the risk of creating progenitor cells with mutated DNA is mitigated. Stem cells are also often compartmentalized in areas of the tissue where they are protected from exposure to chemical mutagens.

Stem cells are generally the least differentiated or specialized cell type. They serve as the precursor cell to a variety of more specialized cell types meaning they are pluripotent or multipotent. Pluripotent stem cells can become any cell in the body, whereas multipotent stem cells are slightly more differentiated and can become a limited number of cell types. Adult stem cells are considered multipotent. Because stem cells give rise to all other cells of that lineage they are prime targets for cancer to hijack them to create tumors.